Thousands of patients, including many young children, become blind from hereditary retinal degenerations. At present no treatments are known for practically all types. In this project, over 1,000 patients with retinitis pigmentosa and allied diseased are on file. Different electroretinograms (ERGs) have been recorded in different genetic types of retinitis pigmentosa. Visually evoked responses (VERs) recorded with a hand-held stimulator-ophthalmoscope in the central fovea were found to be abnormal in many patients with retinitis pigmentosa and all patients tested with juvenile hereditary macular degenerations. Progress has also recently been made in separating the retinal malfunction in gyrate atrophy from that in other forms of pigmentary degeneration and in defining the enzyme defect in this disorder. In sex-linked retinitis pigmentosa, ultrastructural findings in postmortem donor eyes have been correlated with electrophysiological findings. In dominant retinitis pigmentosa with reduced penetrance, studies of the focal cone ERG have revealed that regional differences exist in the temporal aspects of the b-wave in young affected patients. Delays in cone ERG b-wave implicit time seen in patients with retinitis pigmentosa have been simulated in studies of a nutritionally induced retinal degeneration in the cat. The role of the amino acid, taurine, on photoreceptor cell function has been established, and the mechanism by which taurine depletion leads to electrophysiological abnormalities and photoreceptor cell death is under study. Other lines of investigation include recording of the early receptor potential in animals with retinal degenerations and the study of possible toxic effects of drugs on the retina.